In todays active, mobilized society noise has become a common problem. No where is this felt more than when one is trying to fall asleep. In an effort to aid in sleeping the use of sleeping tablets has mushroomed. As is well known, however, this approach to the problem often creates physical and psychological side effects.
For this reason it was early on considered advantageous to induce sleep by physical methods. One such early method was to use electrodes to apply rectangular pulses. Another development was to create a hypnotic effect with lights, i.e., alternately dimming and brightening of a light source. Recently it has been recognized that white noise broadcast as a hum, for lack of a better worded description, can be quite effective as a sleep inducer. It is to the improvement of such an anlgesic nosie generator that this invention is directed. To that end the invention of patent application ser. No. 606,708 filed Aug. 21, 1975 now U.S. Pat. No. 3,993,043 assigned to the common assignee was conceived.